Cu2IrO3: A New Magnetically Frustrated Honeycomb Iridate.
Mykola AbramchukCigdem Ozsoy-KeskinboraJason W KrizanKenneth R MetzDavid C BellFazel TaftiPublished in: Journal of the American Chemical Society (2017)
We present the first copper iridium binary metal oxide with the chemical formula Cu2IrO3. The material is synthesized from the parent compound Na2IrO3 by a topotactic reaction where sodium is exchanged with copper under mild conditions. Cu2IrO3 has the same monoclinic space group (C2/c) as Na2IrO3 with a layered honeycomb structure. The parent compound Na2IrO3 is proposed to be relevant to the Kitaev spin liquid on the basis of having Ir4+ with an effective spin of 1/2 on a honeycomb lattice. Remarkably, whereas Na2IrO3 shows a long-range magnetic order at 15 K and fails to become a true spin liquid, Cu2IrO3 remains disordered until 2.7 K, at which point a short-range order develops. Rietveld analysis shows less distortions in the honeycomb structure of Cu2IrO3 with bond angles closer to 120° compared to Na2IrO3. Thus, the weak short-range magnetism combined with the nearly ideal honeycomb structure places Cu2IrO3 closer to a Kitaev spin liquid than its predecessors.